Electromagnetic transducer



March 20, 1962 D. 1. CARPENTER 3,026,379

l ELECTROMAGNETIC TRANSDUCER Filed Aug. 13, 1958 Z7 W M 7M We W UnitedStates Patent O 3,026,379 ELECTROMAGNETIC TRANSDUCER David J. Carpenter,Perknsville, Vt., assignor, by mesne assignments, to Ex-Cell-OCorporation, Detroit, Mich., a corporation of Michigan Filed Aug. 13,1958, Ser. No. 754,762 7 Claims. (Cl. 179-1002) This invention relatesto magnetic intelligence recording and reproducing devices in general,and in particular to improvements Vto the electromagnetic transducers orheads employed in said devices to impart the recording to the movableintelligence storage medium or to read therefrom such impartedintelligence.

The principal object of the invention is to provide an improvedtransducer head structure in which the transducer core is ixedlysupported in a casing to achieve and retain the desir-able correctalignment of the transducing gap transverse of the direction of themotion of the medium.

Another object of this invention is to provide a head which may beassembled in a unitary structure from components which are easilymanufactured to provide a transducer having constant magneticcharacteristics.

A further object of this invention is to provide a transducer head thatcan be assembled utilizing various previously manufactured coils.

Another object of this invention is to provide a head wherein the coreat the pole tips may be provided with magnetic shielding. A

The various features of the invention will be described in embodimentsthereof with reference to accompanying drawings in which:

FIG. l is a side sectional view of a head of this invention.

FIG. 2 is an end view viewed from left of FIG. l.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1.

FIG. 4 is a plan view of a magnetic core piece.

FIG. 5 is a side sectional view illustrating a variation of theinvention in a dierent embodiment.

FIG. 6 is an end view viewed from left of FIG. 5.

FIG. 7 is a fragmental sectional View taken along line 7--7 of FIG. 6.

In FIG. l a body 11 and a cap 12 together constitute a casing 13 for thehead components. The body 11 is generally tubular and has a central holeenlarged at one end by a counterbore 14 which is adapted to retain alead connector or the like. The exterior of the body 11 is provided witha flattened reference surface portion 10, for the purpose of positioningthe transducer with reference to the record medium as described in thecopending application Serial No. 684,278, filed September 16, 1957 by H.Taft assignor to the same assignee as the present invention, and whichhas now matured as Patent No. 3,001,181, issued on September 19, 1961.The end of the body 11 opposite counterbore 14 has on its exterior areduced diameter portion 15 terminating in a shoulder 16. The same endof the `body 11 includes a recess 17 running crosswise of the body, anda keying slot 18, disposed transversely thereto (FIG. 3). The sides ofthe recess and the slot are located at right angles relative to eachother, and the flattened portion 10 is oriented parallel to slot 18 asviewed in FIG. 2.

The cap 12 has the same outside diameter as body 11 and also has acylindrical bore 20 adapted to snugly tit over the reduced portion 15.Cap 12 includes an inwardly tapering ange portion 21 which terminates ina hole 22 in the end portion thereof.

FIG. 4 illustrates a half core 24 made of suitable material, such asferrite or the like, as is well known in the art.

Mice

Two such half cores are employed in each head and the other half core isindicated in phantom. The half core 2,14

is generally U-shaped having two legs connected by al web and has athickness to snugly fit in slot 18 (FIG. 3). One leg of the core isshaped to form a pole piece with a flux gap defining face 25 and theother leg 23 terminates in a surface 26 adapted to be positioned incontact with the like surface of a complementary mating core in thecompleted assembly. To initially deiine and permanently secure thedesired ux gap, a sliver shim 27 of suitable material, e.g. silver, andof proper thickness is inserted between faces 25-25 of the half cores24. A coil 28, that may be previously manufactured, may be placed overthe leg 23 and within the recess 17 to complete the assembly ofelements.

The transducer head may be assembled by pasting the Sliver 27 to theface 25 of a half core 24 and slipping the coil 28 over its leg 23. Theleg 23 of a second half core 24 is then inserted in the coil until thesurfaces 26-26 are brought in intimate contact with eachother and face25 of this second half core a-buts sliver 27. This now forms asub-assembly, being the magneto-electric operative portion of thetransducer, which is inserted in the body 13 where slot 18 provides aseat for the cores 24-24 and the cavity partly formed by recess 17affords space for the coil 28, the leads thereof passing towardscounter- `bore 14. The cores may be cemented to the sidewalls of slots18. The cap 12 is then pushed over the reduced body portion 15, and thetapered interior portion 21 of the cap abuts complementary taperedportions of the cores 24-24 to securely hold the sub-assembly with thecores abutting the bottom portions of slot 18. The completed assemblymay then be potted in a manner well known in the art, i.e. theinterioris lled with a suitable thermo-setting plastic or the like Iinliuid form and cured.

The flattened surface 10, according to aforesaid Patent No. 3,001,181,is for the purpose of orienting the magnetic linx gap between the polepieces of the core transverse of the direction of movement of the trackof the storage medium when the head -is assembled in its support. Tofully utilize the capacity of the record medium it is desirable that therecording tracks thereon be spaced as close as possible, and to inhibitcross-talk between adjacent transducers it is of utmost importance thatthe magnetic ux gap be exactly aligned along the recording track,particularly when two heads are applied to the same track, e.g. whenusing separate write and read heads spaced along the track. Further,because of aforesaid close track spacing it is desirable to magneticallyshield the pole pieces. A variation of the present invention to fulllthe requirement of orientation and shielding is shown in the embodimentof FIGS. 5, 6 and 7.

In this embodiment all the elements are generally similar to thosedescribed in FIGS. 1 through 4 with the difference that a cap 52 hasbeen substituted for cap 12. The cap 52 differs from the cap 12 in thatthe inwardly tapered ange portion 21 terminates in a wall portion 51ciose off the end of the cap. This wall 51 contains a slot 58 adapted tofit snugly against the pole piece tips of the half cores 24-24 andsubstantially surrounds these tips. In the completed assembly the slot58 will then serve as an effective guide to orient the pole piece indesired manner, and by choosing a material for the cap which has highpermeability, e.g. Mu-metal, the desired shielding eect is achieved. Asecond slot 59 may be provided as shown in FIGS. 6 and 7 to provideclearance for shim 27 and to facilitate the potting operation. When theassembly is completed the cap and the pole piece tips may be machined toafford a clearance of the head relative the recording medium such thatonly the pole piece tips and the immediate portion of the cap protrudewithout departing from the spiritdand scope of the inven-V tion asYdefined in the appended claims.

I claim:

1.. An electromagnetic transducer head for coaction with a magneticintelligence recording-reproducing device comprising; aY magnetic core-in two sections of generally U-shaped form, one leg of said U forming apole piece, and the other leg of. said U forming the other pole piece,said sections mounted such that the extremes of the pole piece legsfaceeach other in spaced relationship to provide a magnetic ux shaping` gapandthe extremes of the other legs abut eachother, a Wound magnetizingcoil surrounding Vsaid abutting legs, a casing body of tubular form,means defining a referencing keying slotV in one end of said casingbody, the keying slot cooperating with the4 magnetic corel for orientingtheV core with respect to the lbody,and a cap fitted over 4the body toholdthe core within said slot. v

2. An electromagnetic transducer head as defined inV claim 1 wherein theexterior of the vbody is provided with a at loc-ating reference surfaceportion extending in one direction substantially parallel to the bodyaxis and in the' otherKV direction parallel to said slot. Y

3.v A magnetic transducer head as deiined in claim l wherein an' openended recess is provided in the' same end the slot said recess -beingpositioned at right' angles to theV slot being adapted to receive andycontainsaid wound magnetizing coil.

4, A magnetic transducer heady as d'eiinedA in claim 1; wherein the bodyand the cap are o` thev same outside diameter tofor-m -a unitarystructure of general cylindrical form providing an envelope for the corewith its pole pieces in proximity of one extreme and having provisionsin the other extreme to attach leads for the magnet-izing coil.

5. An electromagnetic transducer head having a core in two sections eachbeing of substantially U-shaped configuration, the end faces of the-irst legs of the substantially U-shaped core sections ybeing positionedto form ama-gnetc ux shaping gap, and the extremes ofthe second legs ofthe substantiallyV U-shaped 'core sections being in intimate contact, amagnetizing coil surrounding said second legs, a tubular casingbodyprovidedwith a keying slot in one end thereof, said' keyingY slotVproviding', a` seat' Vfor theV said core and orienting the samecentrally and radially with the legs forming the iiux shaping gapprotruding outside the extreme of the body, a partially closed end caphaving a slit thereinV telcscoped over the body in a manner that betweenan interior portion of its closed end and the bottoney of said keyingslot the core is iixed axially, said slit in the closed end surroundingthe protruding legs.

6. A magneticl transducer head asl deiined in claim 5 wherein the coreterminates ilush with the outer end surface of the cap.

7. A magnetic transducer headV as deiined in claim 6 wherein said cap ismade from material of high permeability to provide magnetic shieldingfor the core.

References Cited' inthe le of this patent UNITED STATES PATENTS2,523,515 Porter Sept. 26, 1950 2,756,280 Rettingery July 24, 19562,910,544 McNutt Oct. 27, 1959 FOREIGN PATENTS 751,405 Great Britain.lune 27, 1956 1,140,928 France Mar. 1l, 1957

